This invention relates to the removal of radioactive lead and polonium from tobacco.
It has been reported that tobacco and tobacco products, such as cigarettes contain radioactive lead and polonium. One explanation for the presence of these radioactive elements in tobacco is the accumulation of submicron atmospheric particles containing these elements on the sticky exudate of the glandular heads of the hairlike trichomes which protrude from the tobacco leaves. The radioactive materials then diffuse into the open cellular structure of the glandular heads. During curing of the tobacco, the exudate is thought to polymerize into an insoluble substance encapsulating the trichomes. See Edward A. Martell, "Radioactivity of Tobacco Trichomes and Insoluble Cigarette Smoke Particles" published in Nature, Vol. 249 No. 5454, pp. 215-217, May 17, 1974. Other modes of entry into the tobacco plant, for example, root uptake from the soil and deposition from rainfall, have also been proposed. Studies have also shown that the radioactive metals have been detected in cigarette smoke and in bronchial tissue sites in smokers at higher concentrations than in non-smokers. From this it is speculated that the radioactive elements in tobacco might be a contributing factor to cancer and arteriosclerosis. See Edward A. Martell, "Tobacco Radioactivity and Cancer in Smokers," American Scientist, Vol. 62, No. 4, July-August 1975, pp. 404-412.
Treatment of tobacco to remove potentially harmful chemicals has been an active area of research in recent years. Most of this work has been directed to the reduction of tar and nicotine in tobacco. Some work has been directed to removal of other chemicals such as phenols, benzo (.alpha.) pyrene and metal carbonyls. U.S. Pat. No. 3,246,654 to Oliver W. Burke, Jr., Apr. 17, 1966, relates to removing metal carbonyls from tobacco smoke by contacting the smoke with organic phosphorus compounds. Sugita and Yoshizawa teach in Nippon Senbai Kosha Chuo Kenkusho Kenkyu Hokoku No. 108, 313-17 CA:66 559h that the nicotine content of tobacco leaves can be reduced by dipping the leaves in a 0.35% solution of various chemicals for two minutes. The chemicals reported to have been used are ammonium and sodium polyphosphates. U.S. Pat. No. 3,577,997 to M.A.H. Bindig, May 11, 1971, relates to removing benzo (.alpha.) pyrene by treating tobacco with an aqueous solution of citric acid and deuterium oxide. The treatment is conducted by spraying the solution onto cured, shredded tobacco. W. A. Smith reports in Queensland Journal of Agriculture Science, Vol. 16, No. 3pp (September 1959) that excessive arsenic residues resulting from the use of lead arsenic insecticide were removed from green tobacco leaves by dipping the leaves in 0.25% hydrochloric acid containing 0.25% of a secondary alkyl sulfate detergent. Smith goes on to report that other factors would limit commercial use of this method, and that the treated tobacco leaves were distinctly papery.